CCleaner (formerly Crap Cleaner), developed by Piriform, is a utility program used to clean potentially unwanted files (including temporary internet files, where malicious programs and code tend to reside) and invalid Windows Registry entries from a computer.[8] A public version 1.09 for OS X has been released[6] along with a commercial Network Edition.

CNET editors gave the application a rating of 5/5 stars, calling it a 'must have tool'. It was awarded Editor's Choice Award in April 2009 by CNET.[14] As of January 2014, it has been the most popular software on FileHippo for more than a year, and also has a 5-star editor's rating on Softpedia.[15]